During a surgical operation, certain instruments implements and/or equipment must be held in a stationary position. Such instruments, implements, and/or equipment may include, chest spreaders, suction devices, lights, retractors or clamps. Because the surgeon and his or her assistant need unobstructed use of their hands, such instruments, implements and/or equipment are usually supported in place by conventional mechanical means which are releasably mounted on a rail provided on the operating table or some other stationary object. Various attaching devices for this purpose have heretofore been provided; however, they have generally been of the screw type, which includes a manually adjustable tightening bolt. Due to certain design characteristics these prior attaching devices have been beset with one or more of the following shortcomings: (1) because germs and bacteria can accumulate in the small crevices of the threads formed in various components thereof, proper cleaning and sterilizing of such components becomes a difficult and time-consuming operation; (2) typical screw or bolt type fasteners utilized in such devices inhibit quick attachment, release and/or mobility thereof so as to effect attachment or detachment of the device to a supporting member; (3) such devices require a person possessed of good dexterity and finger strength to effect a secure and stable attachment of the device to a supporting member; (4) the attaching devices are required to be assembled onto one end of the rail and then slid sidewise along the rail to the desired location prior to the start of the surgery; thus, if during the surgery an extra attaching device is required between two devices already supporting instruments, one device must either be disassembled from the rail and then reassembled thereon or the secured instrument must be transferred to another device; (5) previous devices are difficult or impossible to secure over sheets or shrouds customarily used in an operating environment; (6) previous devices are limited for use exclusively with a particular type or style of rail or supporting member.